The Clinical Study Center is a 9-bed multicategorical research unit with specialized nursing, dietary, and supportive staff to provide optimal control of diet, activity and the continued careful observations required for clinical investigation. Principal areas of research are in hypertension, adrenal disorders, anemias, gastrointestinal disorders and chronic renal failure. 1) The role of the renin-angiotensin-aldosterone system in hypertension is under continuous study. The circadian patterns of plasma aldosterone sharpen the differential diagnosis between adrenal tumors and adrenal hyperplasia and other types of hyperaldosteronism with and without hypertension. 2) Also studied are the factors regulating the level of mineralocorticoid hormones, aldosterone, deoxycorticosterone, corticosterone, and their contribution to hypertensive diseases and electrolyte disorders. 3) Intermediary metabolism in the megaloblastic anemias. 4) The mechanism and control of the hyperoxaluria in ileal disease or after resection is an active project. 5) The role of renin deficiency in chronic renal failure is an area of emerging importance. Resultant hypoaldosteronism can lead to potentially dangerous hyperkalemia. Amino acids and nutritional supplementation are being used in children with uremia to improve growth. 25 OH-cholecalciferol is being tested in uremia as a possible therapuetic agent to retard bone demineralization.